Problem: 

In the case that a user is trying an additive input of character(s) to the text area occupied already with the characters at its maximum,  inputting is received. Then, the character(s) already inputted begin(s) disappearing from the last one. 

Especially, in the case of the text area with the vertical scroll bar, a user often doesn't notice the disappering character(s) at the last.

So, unexpected saving behavior with unintended contents can happen.

Solution(Idea):

When adding characters in text area occupied at the maximum character length, 

make it possible to decline the additive input in such a way as allerting with the text " Inputted characters reached to the maximum (500 characters)"